Can we skip the next presidential debate and just have the vice presidential candidates again next week? Vice President Joe Biden and Republican nominee Paul Ryan both showed their value to their respective tickets in an engaging but informative debate that clearly defined their differences on issues.

Each man had a different job to do. Biden needed to fire up Democrats who were downcast after President Barack Obama’s stone-cold performance last week. Biden, known as a motor mouth, also needed to make sure it didn’t backfire on him. He did well on the first count, and got mixed reviews on the second.

Biden grinned and laughed as Ryan was speaking during the first part of the debate, which focused on foreign policy. He frequently interrupted Ryan, blustering at one point, “That’s a bunch of malarkey.” The motor really started running when Biden launched into a rant about presidential nominee Mitt Romney’s much-maligned comments on the 47 percent of Americans who don’t pay taxes.

Biden, a foreign policy expert, easily pushed back Ryan’s criticism that the U.S. was taking the wrong path toward a 2014 troop withdrawal from Afghanistan. Ryan also struggled to explain why the U.S. was not doing enough to stop Iran from getting a nuclear weapon. He kept referring vaguely to “credibility” as the way a Romney administration would push Iran into giving up its quest for a nuclear weapon.

However, Biden didn’t clearly answer why there was not adequate security at the American consulate in Benghazi, Libya, or why the Obama administration described the attack as stemming from a protest over an anti-Islamic video. He said no one had asked for more security, and that the administration was just repeating what its intelligence forces were saying. That was unsatisfying.

Ryan, a first-timer when it comes to national debates, had a slightly lower bar. He needed to show he could match Biden, a debate veteran, and avoid blowing the gains Mitt Romney made in the last debate. Ryan looked like he was debating his grandpa, but he clearly had a grasp of foreign and domestic issues.

Surprisingly, he seemed less clear about the Romney agenda on the budget and taxes — his forte — than on some of the foreign policy questions. Moderator Martha Raddatz was practically rolling her eyes while trying to get Ryan to explain how the math works for the Romney tax plan. And Biden scorched him badly when he said Ryan wrote letters on behalf of constituents seeking money from the stimulus program that he has derided as a failure.

Does it matter? I saw Charlie Cook from the Cook Political report on television before the debate, saying it should come with a disclaimer that the program was “for entertainment purposes only.” The debate was both entertaining and informative, but it didn’t reshape the landscape of the campaign. Obama still goes into next week’s debate with something to prove.